Hollywood’s production companies and the Writers Guild of America have started potentially explosive negotiations, with the companies accused of proposing $60 million in rollbacks.

The first bargaining session started Monday morning at the headquarters of the Alliance of Motion Picture and Television Producers in Sherman Oaks with no comment from either side.

But the WGA launched an attack on the AMPTP last week — offering a sharp contrast with the below-the-radar style of the Directors Guild of America, which concluded a three-year deal with the companies in November.

The WGA’s negotiating committee co-chairs Billy Ray (“Captain Phillips”) and Chip Johannessen (“Homeland”) alleged in a letter to members that the companies had proposed a $32 million cut in pension and health contributions and an $11 million reduction in screenplay minimums over the three-year term of the successor deal.

The AMPTP has not responded to the missive. Ray and Johannessen explained that the companies are proposing the cuts at a time when profits have soared for the AMPTP member companies.

“These proposed rollbacks for writers come at a time of unprecedented prosperity for the studios,” the missive asserted. “The collective profits of our 6 major bargaining partners (Disney, CBS, Comcast, Fox, Time Warner and Viacom) just hit a record $40 billion. This prosperity is based on our work, we are the creative force driving it. Are $60 million in rollbacks a just reward?”

The letter also repeated the key goal of WGA leaders will be to hike compensation for writers on cable shows in order to achieve parity with those on primetime network shows.

Negotiations are starting three months before the current WGA master contract expires on May 1.

Gains in the DGA deal include an annual 3% wage increase; increased residuals bases; significant improvements in basic cable; the establishment, for the first time, of minimum terms and conditions for high-budget new media made for subscription video-on-demand such as Netflix; and establishment of a formal diversity program at every major TV studio.

The WGA staged a bitter 100-day strike in 2007-08 following months of angry exchanges with the late AMPTP president Nick Counter.

During negotiations in 2011, WGA largely eschewed public comment about the negotiations and — as with the DGA, SAG and AFTRA deals — achieved a 2% hike in minimums and a 1.5% increase in employer contributions to the pension and health plans. Concessions included a freeze on primetime residuals and the end of first-class air travel to sets less than 1,000 miles away.